1. Field of the Invention
The present invention relates to a cam assembly for use in a pressing machine to permit a piercing punch or any other machining tool to effect a required pressing or machining on a workpiece, which cam assembly can reciprocate the metal mold or machining tool laterally or obliquely in synchronous with the rising and descending of the upper frame of the pressing machine.
2. Description of Related Art
A certain pressing machine is capable of conducting different workings such as bending, cutting and boring in a single pressing step, and such a pressing machine is equipped with a cam mechanism to permit a selected machining tool to reciprocate laterally or obliquely in synchronous with the rising and descending of the upper frame of the pressing machine. Referring to FIG. 4, the pressing machine has a lower metal mold 2a fixed to its stationary base 1 and an upper metal mold 2b fixed to its rising-and-lowering frame 3, and it has a cam assembly "C" arranged adjacent to the metal mold 2 for converting the rising-and-lowering movement of the frame 3 to the oblique movement to be given to the machining tool.
Referring to FIGS. 5 and 6, such a cam assembly "P"comprises a lower cam 4 to be fixed to the stationary base 1 of the pressing machine (see FIG. 4), a sliding cam 5 slidably coupled to the lower cam 4 and a cam holder 6 slidably coupled to the sliding cam 5 to slidably hold the same. The lower cam 4 has an inclined surface 4a formed on its top. As shown in FIG. 5, the inclined surface 4a has a plurality of recesses made thereon and filled with solid lubricant material to provide an oilless-lubricated surface. The sliding cam 5 has a machining tool (not shown) to be mounted to its front surface, and it has a slider 7 fixed on its rear inclined surface. The slider 7 has a plurality of recesses made thereon and filled with solid lubricant material to provide oilless-lubricated surfaces, thereby assuring that the sliding cam 5 can slide smoothly in the cam holder 6. As seen from FIG. 6, the slider 7 has two longitudinal recesses opening at its upper side, and two coiled springs 8 are inserted in these longitudinal recesses, thereby biasing the sliding cam 5 obliquely downward to the initial stress-free position as shown in FIG. 6.
The cam holder 6 is fixed to the upper frame of the pressing machine, and the cam holder 6 and the sliding cam 5 are so combined as to leave a predetermined space defined therebetween, thereby permitting the sliding cam 5 to be movably held in the cam holder 6. The sliding cam 5 is operatively combined with the lower cam 4 to reciprocate on the inclined surface 4a of the lower cam 4 synchronously with the rising and descending of the upper frame 3 of the pressing machine. Thus, the rising and descending of the upper frame 3 of the pressing machine is converted to the oblique reciprocation of the sliding cam 5 on the lower cam 4.
The sliding cam 5 has a machining tool such as a piercing punch mounted to its front surface 5a as seen from FIG. 4. Such a machining tool can be reciprocatingly moved to and from a workpiece on the pressing stage to effect a required machining such as bending or boring on the workpiece. In pressing, first the upper frame 3 of the pressing machine is lowered along with the cam holder 6 and the associated sliding cam 5, and when the sliding cam 5 abuts on the inclined surface 4a of the lower stationary cam 4, the sliding cam 5 is made to start from the initial stress-free position, moving the predetermined space obliquely upward in the cam holder 6 while compressing the coiled springs 8, which are placed between the cam holder 6 and the slider 7. Then, the sliding cam 5 moves obliquely downward on the inclined surface 4a of the lower cam 4 so that the machining tool may be put in working position relative to the workpiece to effect a required machining such as bending or boring.
Here, it should be noted that the front surface 5a of the sliding cam 5 must be subjected to a required machining to permit the mounting of a selected machining tool thereto (for instances, tapped holes or knock-out pin holes must be made in the front surface 5a of the sliding cam 5). The front surface 5a of the sliding cam 5, therefore, must be subjected to such a machining every time the machining tool is changed.
Disadvantageously such a required machining cannot be effected without disassembling and separating the sliding cam 5 from the cam assembly. If such a required machining is effected on the front surface 5a of the sliding cam 5 in situ, it would move under the resilient influence exerted by the springs 8 when a machining force is applied thereto. The tool-mounting surface 5a, therefore, is too unstable in position to permit the machining thereon. Thus, the required machining is, in fact, effected on the sliding cam 5 after removing it from the cam assembly. This, however, is a tedious, time-consuming work: disassembling the cam assembly to remove the sliding cam 5; machining the sliding cam 5; assembling the so machined sliding cam 5 and associated parts into a cam assembly; setting the cam assembly in position in the pressing machine; and making fine adjustments or trimmings on the machined areas of the tool-mounting surface 5a. The sliding cam 3 is heavy, for instance, 20 kilograms in weight, and the springs 8 when compressed exert a relatively strong force, for instance, beyond 60 or more kilograms. The weight and the counter force make the work still more difficult.